Someone's naked the other side of the vines; what sex are they?
Can't tell? Then the vine canopy has too many leaves.
Least that's the way Dr Richard Smart put it. He's an expert on what's called "canopy management".
No, it's not anything to do with putting up tents. Rather how the winegrower works out what's the ideal environment to ripen their grapes.
Too many leaves can make the shaded bits 10 degrees (Celsius) cooler than at the surface. Grapes deprived of sunlight will develop slower, contain high acid and low sugar levels, and might not ripen by autumn.
That's not good. The pH of the juice will likely be higher, causing problems with fermentation. The resulting wine won't feel balanced in the mouth.
Too much sunlight and the grapes can get sunburn, causing the skins to fracture and let in rot. They can also gain phenolic characters (bitterness, too tannic) which you don't want.
And you thought making wine was a simple, "natural", process? Far from it.